Steel plates covering a subway construction site failed to withstand the impact of a controlled blast that sent rocks flying into the street and damaged nearby buildings, the city's transit authority said Wednesday.
Construction workers were blasting through rock to create an escalator for Manhattan's planned Second Avenue subway when two 1,800-pound steel plates were lifted into the air, allowing debris to rain onto the street.
The cover was supposed to absorb the pressure but didn't, said Michael Horodniceanu, president of capital construction for the Metropolitan Transportation Authority, which runs the nation's largest mass transit system.
Horodniceanu, president of capital construction for the MTA, said that holes for explosive power were drilled at a 30-degree angle, and that was enough of a horizontal that the force of the blast went to one spot that was only covered by steel plates. The blast lifted the plates open and allowed debris to explode onto the street.
"I'm not jumping and blaming anyone," he said. "I will say to you that the responsibility for blasting properly, and all of the means and methods, belong to the contractor."
The contractor doing the blasting for the Second Avenue subway is a three-company consortium called Schiavone, J.F. Shea and Kiewit.
Typically, if a hole is drilled vertically, the energy of the explosion dissipates to the sides and if a hole is drilled horizontally, the energy of the blast goes vertically. Horodniceanu said workers had drilled at the 30-degree angle before without a problem and it was acceptable practice.
Still, the MTA said it will hire an independent safety consultant to review all blasting protocols. The authority is also expanding the safety area around where blasting will occur.
No one was injured by Tuesday’s mishap. The MTA has suspended construction on the 72nd Street Station until it completes an investigation into the explosion and all protocols have been reviewed for safety.
The cost of the consultant is not expected to increase the cost of the project, or delay the project's December 2016 completion.
The MTA said it has done 72 prior blasts on the same corner without incident.
With the Associated Press